For example, it has been carried out conventionally as an immunoagglutination measurement method that the presence of an analyte is confirmed or the concentration of an analyte is measured from the degree of the agglutination generated with the use of an insoluble carrier such as a latex immobilized an antigen or an antibody reacting with the analyte, in order to determine the presence or the concentration of the analyte in a biological sample such as serum, plasma, and urine.
In this immunoagglutination method, an immunoagglutination enhancer which facilitate the generation of agglutination based on an antigen-antibody reaction is usually employed for the purpose of improving the sensitivity. As said immunoagglutination enhancer, polyethylene glycol (PEG) and the like have been known well, however, the PEG has a problem such that the PEG salts out in a solution with high salt concentration, causing a blank value increased, and therefore accuracy of determination becomes worse.
And so, the use of a polymer containing methacryloyloxyethyl phosphorylcholine (MPC) as an immunoagglutination enhancer which solves such problem has been devised (Patent Literature 1).